A high proportion of stomach cancer patients who are below the age of 60 suffer from a specific and genetically unique form of the disease that spreads much more rapidly and is resistant to traditional chemotherapy, a new study has found.

The Mayo Clinic research that was published in the journal Surgery points towards the increasing rates of early-onset stomach cancer which now constitutes more than 30 per cent of all the diagnosed cases. This comes amid the gradually decreasing rates of stomach cancer among older patients.

“I think this is an alarming trend, as stomach cancer is a devastating disease,” said senior author Travis Grotz, M.D., a Mayo Clinic surgical oncologist. “There is little awareness in the US of the signs and symptoms of stomach cancer, and many younger patients may be diagnosed late — when treatment is less effective.”

The research team studied 75,225 cases using several cancer databases to review stomach cancer statistics from 1973 to 2015. Today, the average age of someone diagnosed with stomach cancer is 68, but people in their 30s, 40s, and 50s are more at risk than they used to be.

Although there’s no clear cutoff age for the definition of early-onset and late-onset stomach cancer, the researchers found the distinctions held true whether they used an age cutoff of 60, 50 or 40 years. The researchers found that the incidence of late-onset stomach cancer decreased by 1.8 per cent annually during the study period, while the early-onset disease decreased by 1.9 per cent annually from 1973 to 1995 and then increased by 1.5 per cent through 2013. The proportion of early-onset gastric cancer has doubled from 18 per cent of all cases in 1995 to now more than 30 per cent of all gastric cancer cases.

“Typically, we see stomach cancer being diagnosed in patients in their 70s, but increasingly we are seeing 30- to 50-year-old patients being diagnosed,” Dr Grotz says. The increased rate of the early onset disease is not from earlier detection or screening, Dr. Grotz added. “There is no universal screening for stomach cancer, and the younger patients actually presented with late-stage disease than the older patients,” he said.

In addition to being more deadly, early-onset stomach cancer is also genetically and molecularly distinct, researchers found. Furthermore, traditional risk factors for developing stomach cancer among older Americans, such as smoking tobacco, did not appear to correlate with its early onset counterpart.

“Hopefully, studies like this will raise awareness and increase physician suspicion of stomach cancer, particularly in younger patients,” Dr Grotz said. Younger patients who feel full before finishing a meal, or have reflux, abdominal pain, unintentional weight loss and difficulty eating should see their health care provider, he added.

Stomach cancer is the 16th most common cancer in the US, according to the American Cancer Society. It has a five-year survival rate of 31.5 per cent, and there will be an estimated 27,510 new cases in 2019, according to the National Cancer Institute. The World Health Organization reports that cancer was the second leading cause of death globally in 2018 and that stomach cancer was the third most common cause of cancer death that year.

Next, the research team hopes to better identify risk factors for early-onset stomach cancer using the Rochester Epidemiology Project and potentially other large databases.